Mary Marvel made her debut in Captain Marvel Adventures #18, cover-dated December of 1942, in a story that explained that she was actually Billy Batson's twin sister, and could also summon the power of the wizard Shazam by speaking his name. Learn the entire history of Lady Shazam before the new Shazam film hits theaters! Additional research & writing by Diego Nunez - https://twitter.com/Blackcrow521